This proposal concerns the development of the vertebrate head. The tremendous structural diversity of the currently employed model vertebrate systems including fish, amphibians, birds, and mammals, has hindered the creation of broadly applicable models of vertebrate head development. Lamprey (Petromyzon marinus) are situated at the base of the vertebrate lineage, and are widely accepted as representing the sister group to the jawed vertebrates. Given their relatively simple and prototypical vertebrate morphology, lamprey are ideally suited to serve as a system in which to examine the ground state for vertebrate head organization. The proposed studies to clone and examine the embryonic expression of the lamprey homologs of known head-specific patterning genes, including members of the Otx, Emx, and Dlx families will thus provide a framework in which to interpret the more complex developmental patterns observed in model systems. In addition to the biomedical advances afforded by an increased understanding of vertebrate development, these studies should also allow the direct testing of competing theories of vertebrate origins and evolution. The involvement of undergraduate students in all phases of this research will serve to enhance our institutions existing strengths in engaging and mentoring students in conducting and presenting research.